MECHANICAL DESIGN STARTING POINT & CHOICES 2011
These are the mechanical choices chosen for an elementary school design in BIM Studio 2011. I had a very difficult time getting started with the mechanical design (as the mechanical representative in the BIM team is only a second semester mechanical expert). This wiki is to serve as a starting point / reference as to the amount of detail included in both design development & final design stages. There are notes & recommendations of professors & engineering consultants all compiled & organized here.
Also, view this page for more information: The Mechanical Engineer in Early Stages of Design



JOB OF THE MECHANICAL ENGINEER
  • heat
  • cool
  • venitlate


Local Heat Pump:
__http://www.changeair.com/index.php/standard_water_source_heat_pump__
__http://www.changeair.com/downloads/Senior%20Series_Ver1-9.pdf__


Outdoor Air Ventilation:
__http://www.aaon.com/Documents/Featured/Ventilation_Feature_071015.pdf__

Energy Recovery Ventilator:
__http://www.greenheck.com/products/detail/49__
__http://www.greenheck.com/media/pdf/catalogs/ERVeOctober2008_1.pdf__

pg 8
rooftop AHU = most economical

  • avoids huge duct runs & costs mech room to basement


MECH ROOM EQUIPMENT
geothermal water pump
domestic water heater
water softener

GROUND SOURCE

  • analyze soils for bore holes


GEOTHERMAL
  • bore holes
    • sizes
    • analyze soil
  • pipe locations conceptually


100% DEDICATED OUTDOOR AIR SYSTEM
  • less fan energy


VENTILATION CONCERNS
  • kitchen
  • art room closet: pressurize (exhaust more)
  • nurses room


CLASSROOM
  • 20 cfm/person fresh air
  • THERMAL CHIMNEY
    • sized based upon the heat absorption, not diameter (MEEB, pg. 237)
  • ACOUSTICS
    • entire closet must be enclosed, including where duct pops out


ATRIUM
  • supply low
  • return air high ducts pull from ceiling & take down to heat pumps
  • *morning staging area as unique load*
  • FIRE
    • must be considered one space
    • no louvers
    • once activated, doors are controlled to open via handicapped
    • fans up at windows for exhaust (open door before fan)
    • DELUGE sprinklers along wall: wash wall
    • OR louvers above door


ENVELOPE
  • dew point graph with R values


VERTICAL MECHANICAL SHAFTS DETAIL

ENERGY

  • LEED: optimize energy performance, renewable energy [for pat]
  • DOE Website = average energy use / project type
  • Wizard
    • oriented
    • % glass
    • envelope, roof, + walls match
    • = 4 rooms/floor
    • results within 20%





PRESENTATION #3: DESIGN DEVELOPMENT



Touchstones Focus
3. Energy Efficiency
7. LEED Gold or Platinum
9. Thermal Comfort
10. Indoor Air Quality & operable windows

how can i improve & contribute to team

  • CM - use duct covers during construction to ensure indoor air quality when fired up (also for LEED)
  • CM - when choosing glass material, keep infiltration into the building in mind (an initial investment now will have a payback of a few years through maintenance/energy costs)
  • CM - President Obama vowed to have additional incentive to create energy efficiency (government will provide initial investment)
  • arch - building activities
  • arch - recommended sliding 45% vs awning 75%


DESIGN CONDITIONS
Room category (by function & activity)
Schedules

Weather: worst winter, worst summer, avg

energy consumption estimation

COMFORT
system options (criteria based upon big pic)
tasks = heat, cool, ventilate
Central or Local?

  • local
    • Ability to respond quickly to individual rooms
    • by function
    • classrooms: window cabinet high ac unit by aaf,
    • - noise & by-products
  • central (one or several large mech spaces, dist trees, control systems)
    • - noise, heat
    • +maintenance easy without interupting normal activity
    • -breakdown paralyzes entire building
  • Bathroom - two 1x2 ventilation
  • Faculty lounge - three 2x2 square vents
  • Office - 2x2, slot vents along window
  • library
  • vestibule


Central heating or cooling equipment
design change temp = inside - outside
state college winter design dry bulb = 7degF

ordinary equipment = 500ft2/ton
high-efficiency chillers = 1000ft2/ton

HEALTH
indoor air quality

  • duct covers during construction (LEED)
  • locate air intakes above pollution
  • zoning: copier
  • passive low-energy approach to ventilation = windows (give building occupants control over outdoor air)
  • pollutant sources: odors, irritants, toxic, biological, radon
  • dirty vs. clearn areas? change pressure


VAV
fan capacity control reduces the energy consumed by fans which can be a substantial part of the total cooling energy requirements of a building
+ humidification greater


chilled beam
chilled beam uses water to remove heat from a room, based on induction terminal units that were applied in past years
located in room
primarily commercial arena
+ move the chilled water closer to the occupied space
+ attempt to minimize the energy required by fans

- level of humidity control required
vs. variable air volume
- high chilled beam systems costs
- technology risks for condensation & associated water damage

TYPES
chilled
passive
active
multiservice:
can contain lighting fixtures, sprinkler systems, smoke detectors, security sensors, motion detectors, intercoms, power distribution centers, fiber optic distribution centers

LEED
manufacturer

  • ducts: killengers custom sheet metal
  • chilled water pump: armstrong

duct covers during construction

SUSTAINABILITY
involves meeting the needs of today’s generation without detracting from the ability of future generations to meet their needs

energy

  • heat by-product from one = intake of another


comfort, zoning, & equipment

life cycle analysis: systems installed, maintenance, operating costs


prelim evaluation of energy use (suggestions to team about eval)

MECHANICAL RULES OF THUMB
Air Movement
6 ACH


1 CFM/ft²

Ventilation Rate
5 CFM/person

Fan Energy
1000-1500 CFM/hp

Electric Motors
.8-.85 kW/hp

Lighting
2-4 watts/ft²

Chiller Size
300-400 ft²/ton

Ton
12,000 BTU/ton

Chilled Water
2.4 GPM/ton (10° rise)

Condenser Water
3 GPM/ton (10° rise)

Chiller Input
.7-.8 kW/ton

Chillers & Pumps & Towers
.9-1.0 kW/ton

Absorbers
18 lbs steam/ton

Boiler Horsepower
33,479 BTU/hr = 9.8 kW

Rebuilt Systems Design
55°F supply air


30°-40° rise reheat coils

Dual Duct & Multizone Design
55° cold deck


70-105° hot deck - with ODA Reset Schedule

VAV
55°F cooling


10% box leakage flow


40-50% minimum fan volume

People Load
450 BTU/person/hr

People Density
Office
140 ft²/person

Theater
14 ft²/person
Heat Transmission
See ASHRAE Handbook of Fundamentals


Glass
1 BTU/ft²/°F

Good Wall
0.1 BTU/ft²/°F

Masonry Wall
0.15-0.3 BTU/ft²/°F

Thin Poor Wall
0.25-0.5 BTU/ft²/°F

Overall Building
0.15-0.5 BTU/ft²/°F
Infiltration
0.5-1.5 ACH without Building Pressurization



Chiller Efficiencies
Air-cooled (including condenser power > 150 tons)
EER
COP
kW/ton
ASHRAE Standard 90.1 1999
9.6
2.8
1.26
Good
9.9
2.9
1.21
Best
10.6
3.1
1.13

Water-cooled (>300 ton centrifugal compressor)
EER
COP
kW/ton
ASHRAE Standard 90.1 1999
16.7
4.9
0.72
Good
18.5
5.4
0.65
Best
26.7
7.8
0.45